Though well though of and plausible noone of the scenarios you predict may end Humanity. But something unseen and unthought of like a mad man with his finger on the nuclear holocaust... Truth as they is always stranger than fiction. To your credit atleast you did not try the hoax 'world is going to end on dash-dash-dash date that is nothing but garbage from self seeking internet portals and individuals.
Real Ways the World Will End
We all know how awesome a zombie apocalypse will be. But let’s be honest with ourselves: it probably will never happen (sad face). As much as I hate to admit it, real life zombies are not very plausible, and neither is an alien invasion. There are, however, multitudes of ways all human life can be extinguished from our great planet Earth. Here is a list of the most probable ones.
1. The Sun will eventually change to a Red Giant and disintegrate all life in our solar system.
ETA: 1 billion years, give or take a few million.
It is pretty much a sure thing that our Sun will eventually change to a Red Giant. And as our Sun becomes a Red Giant, the surface temperatures will increase slowly until our planet will be too hot for liquid water to exist. Everyone still on Earth by then will most likely have perished, as there is no way for humans to survive in such extreme conditions, and even before surface temperatures reach boiling point, most of our planet will be covered under water as the polar ice caps melt and insane storms will rage throughout the planet.
Can humanity survive?
That will depend entirely on our level of technology a billion years from now. However, I have a sneaking suspicion that within a few thousand years, we will already be colonizing new planets. Then within a few million years, hopefully we will have mastered FTL travel. Cross your fingers and hope that FTL travel is actually possible, or we’ll be living in inhospitable planets for a very long time.
2. An asteroid will hit the Earth and cause a planet-wide extinction similar to the way dinosaurs died.
ETA: We’re safe until 2036; after then, it will be a lottery draw. 625-1 chance in the year 2040.
Normally, if a smaller asteroid only a few meters across heads for Earth, it would most likely burn up or explode in the atmosphere. However, if an asteroid 1 km across or larger were to impact Earth, it would cause mass extinctions. An asteroid 1 km across would have the kinetic energy equivalent to 46300 megatons during impact (by comparison, Little Boy, the atomic dropped on Hiroshima was only 16 kilotons), and leave a 8.5 mile crater. The sheer amount of energy from the impact of an asteroid that large will kick up a lot of dust and debris into the atmosphere and block sunlight from reaching the Earth. Without sunlight, plants will die, and in turn, all other animals in the food chain.
Can humanity survive?
Chances are that a few humans will be able to survive; however, a lot of preparation will be needed. For example, underground hydroponic farms will be required for food until the dust settles and sunlight is once again able to reach the surface of the Earth. Then after the dust settles a few years after the impact, those plants will once again need to be planted on the Earth’s surface to “restart” life. So while this event is most certainly catastrophic, humanity will most likely survive, even if it comes down to only a couple thousand or million people.
3. A rogue black hole will cause the Earth to change its orbit.
ETA: We’ll never know what hit us.
The closest black hole to the Earth is 27,000 thousand light years away. That pretty much means we’re safe and sound for now. However, there exists a possibility that “rogue” black holes roam throughout the galaxy. And if a rogue black hole gets close enough to the Earth, there’s a huge possibility that its immense gravitation pull will be able to affect the Earth’s orbit around the Sun. As of now, Earth’s orbit around the Sun is nearly a perfect circle, with an eccentricity of less than 0.02 (if the eccentricity is 0, the orbit is a perfect circle, and if the eccentricity is 1, the orbit is long and skinny). However, if the Earth’s orbit were to change into a more elliptical shape due to the gravitation pull of a black hole, the seasons on Earth could vary from an extremely cold winter to a blazingly hot summer every year. If the orbit changes enough, it could even mean the end of life on Earth as we know it.
Can humanity survive?
Much like with the sun changing into a red giant, if humanity is capable of traveling to and colonizing other hospitable planets by the time a rogue black hole whips around to kick our butts, then we stand a pretty decent chance of survival. However, while we can somewhat predict the amount of time we have left until the Sun melts the Earth, it’s hard to tell when and if a black hole will come to our side of the universe. If a rogue black hole were, in fact, to come into the vicinity of our solar system, humanity’s survival would depend on the amount of change in Earth’s orbit as well as humanity’s ability to travel to other hospitable planets. If a black hole’s coming our way, there’s no way we could stop it.
4. The Higgs boson will settle onto a new minimal energy, and a new alternate universe will expand and wipe out our current universe.
ETA: tens of billions of years
To give you a brief explanation of how the end of the universe will come about, you first have to know what the Higgs boson is. The Higgs boson, otherwise known as the “God” particle, is an elementary particle with no spin or electric charge that gives off something called the Higgs field. The Higgs field is what give some fundamental particles mass. Herein lies the potential for the end of all life as we know it: if the Higgs boson were to settle onto a new minimum potential energy, then the mass of fundamental particles will change as well. If the mass of the fundamental particles change, all physics as we know it gets thrown out the window. Once this happens, a bubble that is like an alternate universe will randomly appear somewhere and begin expanding at the speed of light and engulf our current universe.
Can humanity survive?
No. Humanity will not and cannot survive this catastrophic event. In fact, anything alive in the entire universe will not survive. No matter how advanced our science becomes billions of years from now, it will still all be based on our current understanding of physics with the current minimum potential energy of the Higgs boson (which is 126 billion eV). Once this value changes and the bubble forms, there will be no way for us to know how the new universe will behave. Fortunately for us, however, since everything will be engulfed at the speed of light, we’ll simply be here one moment then gone the next. Quick and painless.